Shares in SolarCity were little changed on the report, which was published before noon Tuesday.

Based in Provo, Utah, Vivint Solar was launched in 2011. In a recent interview with BI's Jay Yarow, Vivint Solar CEO Todd Pedersen argued his firm had taken just two years to attain a size that it took where SolarCity 8 years to reach. "They'll probably be big, we'll just be bigger, is the bottom line," he said.